// SPDX-License-Identifier: AGPL-3.0-only

//! Unit tests for the pure helpers in [`crate::renderer`].

use super::*;

#[test]
fn far_plane_floors_at_the_minimum_for_near_fog() {
    // Fog that saturates well inside the minimum leaves the far plane at the floor; shrinking it to match would clip geometry for no gain.
    assert!((far_plane_for(128.0, 64.0) - MIN_FAR_PLANE).abs() < f32::EPSILON);
}

#[test]
fn far_plane_covers_the_diagonal_of_the_two_extents() {
    // 768 horizontal and 384 vertical (a radius-24 cylinder) reach 858.6 at the corner, past the 500-block floor.
    let far = far_plane_for(768.0, 384.0);
    assert!(far > MIN_FAR_PLANE);
    assert!(
        (far - 858.65_f32).abs() < 0.01,
        "unexpected far plane {far}"
    );
}

#[test]
fn far_plane_reaches_past_each_extent_taken_alone() {
    // The corner of the box is further than either edge, so covering only the larger extent would still clip partially-visible fragments near the diagonal.
    let (horizontal, vertical) = (768.0_f32, 384.0_f32);
    let far = far_plane_for(horizontal, vertical);
    assert!(far > horizontal);
    assert!(far > vertical);
}

#[test]
fn far_plane_is_well_formed_without_fog() {
    // A caller that supplies no fog distance must still receive a usable projection rather than a degenerate zero-depth one.
    assert!(far_plane_for(0.0, 0.0) > 0.0);
}